1. Field of the Invention
The present invention relates to broadcast receivers, particularly a broadcast receiver that can receive broadcasts utilizing a variable directional antenna.
2. Description of the Related Art
Television broadcasting has the frequency band of VHF (Very High Frequency) and UHF (Ultra High Frequency) allotted. In general, the Yagi antenna is employed for receiving television broadcast signals. The Yagi antenna is constituted of a reflector, a radiator, and a director, and has high directivity towards the director side by the function of the reflector. The merit of large gain is also recognized in the Yagi antenna.
The Yagi antenna is set to have its directivity match the direction of the broadcast station in order to obtain favorable reception. A receiver employing such an antenna carries out the process of searching for a channel valid for reception by that receiver. This process is called “channel search”.
Japanese Patent Laying-Open No. 2004-120057 discloses the technique of searching for a channel, excluding any preset channel, in order to conduct channel search more efficiently.
Since the antenna is generally installed at the roof or the like of a building in a fixed manner, the directivity cannot be readily modified when once installed. In the case where a plurality of broadcast stations are located in a distributed manner, only the broadcast signal of a broadcast station in a specific direction corresponding to the directivity could be received.
In view of the foregoing, there is proposed a variable directional antenna that can have the directivity switched in several directions to allow reception of waves from various broadcast stations that are located in all directions. A smart antenna is known as one of such variable directional antennas. The smart antenna is formed of a plurality of antenna elements. The directivity can be switched by exciting each antenna element at an appropriate amplitude and phase.
The usage of the smart antenna set forth above allows broadcast waves to be received from various broadcast stations even when the stations are located in a distributed manner.
In order to receive waves from the best serving direction by a receiver utilizing such a variable directional antenna, it is considered that channel search must be executed in a manner different from that of the receiver that utilizes a conventional Yagi antenna.
Channel search utilizing a variable directional antenna is generally time consuming. Specifically, the time required for channel search utilizing a variable directional antenna is several times that required for channel search utilizing a unidirectional antenna such as the Yagi antenna. For example, the channel search based on a unidirectional antenna requires approximately two minutes, whereas the channel search executed based on a variable directional antenna switchable in 16 directions for all the channels (for example, when channels 2-69 are set) as well as for all the receiving directions takes approximately thirty minutes. It is therefore considered that some measures must be taken to eliminate inconvenience on the user as to the manner of executing channel search by a receiver that utilizes a variable directional antenna.
However, conventional receivers utilizing variable directional antennas have failed to account for measures related to channel search.